In the United Kingdom and around the world, significant lengths of electrical cable are underground, especially in built-up areas where it is difficult or undesirable to suspend cables from pylons.
In many cases, since these cables were laid, further building has been done above the cables.
At present, in order to remove such cables, it is generally necessary to dig them out. However, this is often extremely difficult, for example where extensive building has been carried out above them and/or where the owner of the land does not wish his land to be disturbed. For example, if the cables pass under farmland, it is often necessary initially to remove and store the topsoil. Then it is necessary to dig out the cable. Once the cable has been dug out, it is necessary to import earth to fill the void left by the removed cable, before replacing the topsoil. Throughout this procedure, the farmer is unable to use his land.
As a result of these difficulties, it is often easier to leave redundant cables where they are.
However, many underground electricity cables include oil under pressure to prevent the high-voltage conductive core becoming inadvertently grounded. This can be an environmental risk since the oil can be environmentally damaging if it leaks. Furthermore, the risk of such leaks is higher with redundant cables since they are generally older and potentially degraded in comparison with newer cables.
One way in which this risk is addressed is by soldering caps onto the ends of sections of redundant cables to prevent leakage of oil. However, this is a costly process and needs to be carried out by an expert jointer.
GB 2466897, GB2431424 and GB2426534 disclose overdrilling devices. DE19802691 and DE19504484 disclose equipment for removing buried cables. Energy Networks Association NIA Project Registration and PEA Document of February 2014 provides details of a project for cable extraction.